Death Cardiovascular Respiratory and Neurologic Mechanisms

Death: Cardiovascular, Respiratory and Neurologic Mechanisms
Mitochondria in tissues unable to utilize O2
Reduced hemoglobin in blood to carry O2
Low oxygen content in blood (CaO2)
Hypoxemia (Type I Respiratory Failure): low dissolved oxygen in blood (PaO2)
Lungs can’t oxygenate blood fast enough
Lungs can’t rid blood of CO2 fast enough
Hypercapnia / hypercarbia (Type II Respiratory Failure): elevated dissolved CO2 in blood (PaCO2)
Cerebral vasodilation
Toxins: e.g. cyanide, pesticides, arsenic Severe anemia
Distributive problems:
Systemic inflammation (sepsis, anaphylaxis, pancreatitis), adrenal insufficiency, vasodilatory drugs
Obstructive problems: Cardiac tamponade*, tension pneumothorax* or massive pulmonary embolism*
Hypovolemic* problems (low blood volume): Hemorrhage, dehydration, widespread skin disruption or burns
Cardiac valve dysfunction
Myocardial infarction* or cardiomyopathy
Cardiac arrhythmia or heart block
Disturbed electrical activity in cardiomyocytes
Peripheral metabolic disturbances
Hypokalemia*, Hyperkalemia* Acidosis* (including renal failure) Hypothermia*
Toxins* (e.g. cocaine, beta blockers, tricyclics) Severe thyroid derangement
Inappropriate systemic vasodilation
Adjacent forces impair heart filling
Low cardiac preload
Low stroke volume (SV; depends on valves, contractility, preload)
Decreased systemic vascular resistance (SVR)
Low blood pressure (BP = CO x SVR)
Decreased cardiac output (CO = SV x HR)
Disseminated intravascular coagulationàwidespread thrombi that occlude blood flow (also causes hemorrhage, see relevant box at left)
Methemoglobinemia: some hemoglobin gets stuck in a state that can’t carry O2
Hemoglobin has reduced capacity to carry or release O2
Drugs: e.g. dapsone, nitrates
Carbon monoxide poisoning
Circulatory collapse / shock: inadequate perfusion of tissue with blood
Respiratory collapse: blood has insufficient useable O2 content
Ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT)
Hypoxia*: inadequate O2 delivery or utilization in tissues
Hypoxia creates metabolic disturbances that impair cardiac cells. Alternatively, any of the preceding conditions marked with (*) can directly trigger cardiac arrest first
Pulseless Electrical Activity (PEA): organized activity on ECG with no cardiac output (can be preceded or mimicked by pseudo-PEA, in which there is still some output on ultrasound)
Low atmospheric pressure or oxygen content Severe lung disease
Asthma, COPD, interstitial lung disease, congestive heart failure, pulmonary hypertension, pulmonary embolism, lung collapse / atelectasis
Acute respiratory distress syndrome
Pneumonia, aspiration pneumonitis, inhalational injury, systemic inflammation, drowning
Severe hypoventilation
Respiratory fatigue, advanced COPD, chest wall disorders, neuromuscular disorders, upper airway obstruction, toxins (e.g. opioids, botulism)
Can degenerate at any time
Asystole: no cardiac electrical activity or output
Respiratory arrest: cessation of breathing
Inability to protect airway
Decreased level of consciousness
This is a broad overview of the many scenarios that can result in death. For detailed explanations of the various disease mechanisms, refer to the corresponding slides.
* = reversible causes of cardiac arrest (Hs and Ts)
Ben Campbell
Yan Yu*
Huma Ali*
* MD at time of publication
(low heart rate, HR)
Unopposed parasympathetic stimulation of heart (can also cause vasodilation, see Distributive problems)
Disruption of spinal cord sympathetic control
Injury to cervical or upper thoracic spinal cord
Irreversible cessation of cardiac, respiratory, and brain function
Prolonged seizure initially causes increased cardiovascular activity, until the system fatigues
Disruption of respiratory control center in medulla
Expanding skull contents squeeze brainstem (herniation)
Increased intracranial pressure
Edema from intracranial hemorrhage, trauma, brain mass
Edema, inflammation, hypoxia and/or metabolic derangements cause diffuse neuron dysfunction
Central nervous system infection
Dementia, particularly with delirium
Massive ischemic stroke
activity prevents or alters breathing
Metabolic disturbances that affect the central nervous system Hypoglycemia Hypocalcemia, hypercalcemia Hyponatremia, hypernatremia Uremia
Acute liver failure (hyperNH4) Many drugs / toxins Withdrawal (e.g. EtOH)
Status epilepticus
Brainstem lesion (e.g. stroke, neoplasm, inflammatory)
Nervous System Insult
Sign/Symptom/Lab Finding
Published November 11, 2023 on
Respiratory System Insult
Cardiovascular System Insult Cardiogenic problems